Accuracy Evaluation of Estimated Ionospheric Delay of GPS Signals Based on Klobuchar and IRI-2007 Models in Low Latitude Region

The required positional accuracy of GPS is limited by several error sources. Among these, the predominant error source is the ionosphere, which introduces error in range measurements of the propagating signal. The intensity of ionospheric delay dynamics depends on solar activity. Also, it is highly variable during the equinoctial period compared to other seasons. The present work reports the statistical comparison of ionospheric delay based on Klobuchar and IRI-2007 models with observed data over the low latitude region during the spring (March and April) and the autumn (September and October) of an unusual solar minimum (2006). Total electron content (TEC) data from three receiver stations of GAGAN network is considered. The observed data results show that the maximum ionospheric delay is 12.14 m at Delhi station. The monthly mean values vary significantly over the considered equinoctial period. The IRI-2007 model ionospheric delay statistics are closer to the observed data than the Klobuchar model for the considered stations. The results are useful for ionospheric delay modeling in the context of satellite navigation systems over the low latitude region.